In the technical field of absorbent articles, considerable efforts have been made over many years to increase the number of manufactured articles, for example babies' diapers or incontinence diapers, per unit of volume for storage and transportation. Nowadays, for example, twice as many babies' diapers are transported by truck as were transported in a similarly sized truck a number of years ago.
Thinner articles, still with a high absorption capacity, represent one of the areas that have been improved. Enhanced thinness has been achieved principally by introduction of gel-forming superabsorbents in increasing concentrations in the absorption cores of the absorbent articles. The articles have thus been improved in terms of their handling both during storage and transportation. Thinner absorbent articles have also been preferred by users, and this fact has of course also prompted various manufacturers to steer developments in this direction.
Thinness has also been achieved by the fact that the articles are nowadays compressed much more than in the past. EP 0,122,042 is one example of a patent which describes how absorbent articles are compressed efficiently so as to achieve increased thinness while at the same time maintaining or even improving the absorption capacity. The patent proposes compressing absorption bodies at a low moisture content in order to maintain softness and pliability despite compression to high density levels (low bulk levels).
More effective ways of packaging absorbent articles have also been developed. The absorbent articles have been packaged with ever greater compression.
Patent application GB 2,264,278 A describes a method for effective compression of a stack, that is to say an individual packaging unit, of absorbent articles in connection with the articles being enclosed in a wrapper. The volume of the packaging is minimized by means of a stack of folded absorbent articles being compressed together with a two-part packaging envelope of the wrapper type. Finally, the absorbent articles are locked in the compressed state by the two parts of the packaging envelope being connected to one another when the absorbent articles are still under external compression.
U.S. Pat. No. 4,934,535 describes an easy-to-open packaging for compressed absorbent articles. The patent also describes how a bag is filled with absorbent articles at the same time as the stack of articles is compressed. When a bag is to be filled with folded absorbent articles, according to the patent, the stack of articles is first compressed by two pressing devices. The pressing devices are then introduced into the bag together with the compressed articles, the articles remaining pressed together throughout the stage of introduction. The surfaces of the pressing devices which are in contact with the stack of articles comprise members which are movable in the depth direction of the bag, and the pressing devices can be removed from the bag without any frictional forces arising between the stack of absorbent articles and the pressing devices. Since no frictional forces arise between the stack of articles and the pressing devices when these are drawn out of the bag, the pressing devices can be removed without any risk of the stack collapsing. When the pressing devices have been removed, the stack of articles is kept under pressure by the sides of the bag. The filling method permits high density of packaging while maintaining a high finish of the packaging.
A problem which is not solved in the patent U.S. Pat. No. 4,934,535 is that of protecting the folded areas of the articles when these are pressed together and stored under high pressure in the packaging.
When a packaging unit comprising absorbent articles folded about one or more substantially transverse fold lines is compressed at right angles to the material layers, the fold areas are the most sensitive areas of the articles. High compression often means that permanent fold notches are formed, and the absorbent article will then have one or more hard and uncomfortable creases when it is being worn by a user. Fold notches also function as channels in which liquid can run, a fact which is particularly unfortunate when the channels extend in the transverse direction of the absorbent article and are located in the area where various body fluids such as urine are collected in the absorbent article.
Compression of other parts of the absorbent articles in the packaging unit, that is to say compression at right angles to the material layers, is not as problematic because no creases or the like are created. In addition, the material layers normally included in absorbent articles have a considerable capacity for recovering their original configuration when the compression ceases, as long as the compression has taken place at right angles to the material layers.